In conventional windable screen devices installed in an opening of a building for insect prevention, light-shielding, or insulation, one end of a screen, such as a fly-screen, is fixed to a movable-frame member, which can be operated to open or close the screen, and the other end of the screen is fixed to a winding shaft provided with a spring which functions as a driving source for winding the screen. Thus, the winding shaft rotates in forward and reverse directions so as to wind and unwind the screen.
In such conventional screen devices, the winding shaft is generally housed in a winding box fixed to one of side-frames disposed along one side of an opening of a building, and a locking-frame member is fixed to the other side-frame disposed along the other side of the opening of the building. Moreover, a locking mechanism is attached to the movable-frame member used for opening and closing the screen. Such a locking mechanism is provided with a hooking component which can be resiliently engaged to an engagement portion provided in the locking-frame member when the screen is pulled out.
However, such conventional windable screen devices have an extremely simple structure and are problematic in that the locking mechanism of the movable-frame member engaged with the locking-frame member can only be unlocked from the inside of the building. For this reason, if a person is outside the building, he/she cannot release the closed state of the screen from the outside. This is problematic in cases where the person might desire to bring in objects through the opening of the building or to simply enter the building through the opening.
Moreover, because the locking mechanism is generally firmly fixed to the movable-frame member in such conventional windable devices, the positional adjustment of the locking mechanism along the movable-frame member is difficult. Performing such an adjustment regardless of its difficulty may result in attachment marks, such as holes and openings, left on the movable-frame member that were used in the previous attachment.